rewards NTP widget isn't updating with estimated ad earnings

[LaurenWags]

Description

Estimated earnings so far this month is not updating on NTP widget.

Steps to Reproduce

1. Clean profile
2. Enable Rewards
3. View some ads

Actual result:

NTP widget does not update

Expected result:

NTP widget should update

Reproduces how often:

easily

Brave version (brave://version info)

Brave	0.73.51 Chromium: 78.0.3904.87 (Official Build) nightly (64-bit)
Revision	20c21f4010010f32462ea8e1d6af30cef66d48c8-refs/branch-heads/3904@{#840}
OS	macOS Version 10.13.6 (Build 17G5019)

Version/Channel Information:

• Can you reproduce this issue with the current release? n/a
• Can you reproduce this issue with the beta channel? n/a
• Can you reproduce this issue with the dev channel? n/a
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? n/a
• Does the issue resolve itself when disabling Brave Rewards? n/a
• Is the issue reproducible on the latest version of Chrome? n/a

Miscellaneous Information:

cc @mandar-brave @ryanml

[GeetaSarvadnya]

Verification passed on

Brave	0.71.111 Chromium: 78.0.3904.87 (Official Build) (64-bit)
Revision	20c21f4010010f32462ea8e1d6af30cef66d48c8-refs/branch-heads/3904@{#840}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified the STR from the description

Verified passed with

Brave	0.71.111 Chromium: 78.0.3904.87 (Official Build) (64-bit)
Revision	20c21f4010010f32462ea8e1d6af30cef66d48c8-refs/branch-heads/3904@{#840}
OS	macOS Version 10.13.6 (Build 17G5019)

• Verified STR from description

Verification passed on

Brave	0.71.111 Chromium: 78.0.3904.87 (Official Build) (64-bit)
Revision	20c21f4010010f32462ea8e1d6af30cef66d48c8-refs/branch-heads/3904@{#840}
OS	Ubuntu 18.04 LTS

• Verified STR from description